This invention relates to gang writing storage disk drives.
Disk drive systems store data magnetically, typically in multiple disks each having two storage surfaces. Millions of bytes of information are stored on these surfaces as binary 1""s and 0""s. In order to efficiently store and retrieve the bytes of information stored on these disks, disk drive controllers need to know locations on the disks where to write data to and read data from. Each location on the disk surfaces is identified by short segments of site information stored at various locations on the disk surface. Using the site information the disk drive can accurately store data to and retrieve data from desired locations on the disk surfaces.
Data are stored in multiple concentric circular tracks on one or more surfaces of the disks. In each track are several spoke areas separated by user data areas. Spoke data stored in spoke areas provide site/position information of associated user data stored in adjoining user data areas. Spoke data are written so that they are readable regardless of a radial position of the heads relative to the disk.
Storing site information for use by the disk drive controller to identify locations on the disk surfaces adds a significant amount of time and cost to the production of the disk drive. Typically, a servowriter is used to write the site information on the disks. The servowriter is a specialized piece of machinery that is expensive, so few servowriters are used to write site information to many disks. This creates a bottleneck in production, with disks waiting to be written with site information. Reducing the time needed by the servowriter to write the site information to each disk can reduce the cost of the disk drives.
According to one aspect of the invention, a method of storing data on a surface of a storage disk, the data being capable of verifying an identity of the surface, includes determining first check data from first alignment correction data associated with a first storage surface. The method also includes determining second check data from second alignment correction data associated with a second storage surface such that the second check data is different from the first check data if the first and second alignment correction data are identical. The method further includes writing the first and second check data to the first and second storage surfaces in association with the first and second alignment correction data, respectively.
According to another aspect of the invention, a method of using a disk drive includes selecting one of two storage disk surfaces that have similar surface identification information stored on the respective surfaces. The surfaces further store check data in association with the surface identification information, the check data of the selected surface being modified check data, representative of original check data. The method further includes reading the modified check data and processing the modified check data, differently than the check data of the nonselected surface would be processed, to recover the original check data.
According to another aspect of the invention, a disk drive includes a plurality of storage disks each storage disk having two surfaces. At least two of the surfaces of the plurality of storage disks include site data stored on the two surfaces, the site data indicative of either of the two surfaces, alignment correction data associated with the site data, and check data associated with the alignment correction data. The check data of a first of the two surfaces has a first relationship with respect to the alignment correction data of the first surface, and the check data of a second of the two surfaces has a second relationship with respect to the alignment correction data of the second surface. The first and second check data are different for identical alignment correction data,
Various aspects of the invention may provide one or more of the following advantages. Time and cost to write data to disk surfaces using a servowriter are reduced. Spoke data can be gangwritten to multiple disk surfaces and the gangwritten surfaces can be distinguished. The identity of a gangwritten surface can be verified within a predetermined certainty before writing to the surface. The likelihood of unintentional destruction of data due to a head-select failure is reduced.